Health Impact Assessment of Short-Term Exposure to Particulate Matter (PM10) in Northern Thailand

In northern Thailand, in recent decades, particulate pollution from the burning of biomass has become a serious issue with toxicological implications for human health, especially during the winter months of January to April. The purpose of this study was to explore short-term exposure to particulate matter (PM10) in northern Thailand. The high PM10 concentration in 2012 was used as a case study. We used the EPA's Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) for the health impact assessment, along with ground-based measurement data. The annual average observed PM10 concentration was in the range of 43–61 μg/m3, with a maximum observed PM10 concentration of 300 μg/m3 in March. We then assessed the impacts of PM10 exposure in northern Thailand. When the PM10 concentration was reduced to 120 μg/m3, the undesirable effects on respiratory mortality decreased by 5%–11%. When the concentration of PM10 was reduced to 45 μg/m3, the deleterious effects on respiratory mortality decreased by 11–30%. In conclusion, adherence to the WHO-AQG, particularly for PM10 (45 μg/m3), tends to result in considerable reductions in respiratory disease mortality in northern Thailand.


Introduction
Air pollution is a major problem and has severe toxicological efects on human health and the ecosystem [1,2]. It is widely recognized that air pollution contributes to the onset of illnesses such as infectious diseases, infammatory disorders, and cancer [3][4][5][6]. It is also responsible for millions of deaths worldwide each year [7][8][9][10].
In recent decades, biomass burning has been a major source of air pollution in northern Tailand, particularly between January and April [11][12][13]. In addition, signifcant haze episodes in this region have become increasingly severe and frequent in recent years due to increased particle pollution. Factors contributing to northern Tailand's air quality problems include emissions from extensive biomass burning and human activities from both domestic and neighboring countries, which release particle pollution [11,[14][15][16]. Moreover, the combination of topographic and meteorological characteristics stimulates environmental conditions that are conducive to and which contribute to the air pollution problem in northern Tailand. People in northern Tailand are subjected to annual periods of biomass burning from agricultural waste and forestry inside and outside Tailand (in neighboring countries), resulting in unusually high particulate pollution from January to April each year [17][18][19][20][21].
Several unfavorable health consequences can arise from exposure to high amount of air pollution. A considerable number of studies of short-term exposure to air pollution have examined the associations between low air quality levels and daily variability in death rates [22,23]. High levels of particulate matter (PM) potentially pose a threat to human health because, based on their size, the inhaled particles may reach critical depths in the lungs, causing detrimental health efects. Several studies have revealed a correlation between high levels of particulate matter and an increase in respiratory and cardiovascular pathologies; for example, the studies conducted by [17,[24][25][26][27] and Kelly et al. [28] suggested that PM 10 levels below the EU Directive 2008/50/EC daily limit (50 μg/m 3 ) are related to an elevated risk of acute cardiovascular events. In addition, the International Agency for Research on Cancer listed outdoor air pollution and particle matter as carcinogenic. Although PM 10 air pollution impacts the entire population, it has been established that children, elderly adults, and those with preexisting health conditions are more susceptible to acquiring specifc illnesses [29,30]. Moreover, PM 10 [31]. During a study period (2006)(2007)(2008)(2009)(2010) in major Chinese cities, a 10 μg/m 3 increase in monthly PM 10 concentration was linked to a 1.05% increase in the adult respiratory death rate [32]. In Shenzhen, China, the excess risk of all-cause death with an increase in PM 10 of 10 g/m 3 was 0.61% (95% confdence interval (CI): 0.50-0.72) [33]. Tese studies suggest that short-term PM 10 exposure has signifcant public health impacts.
A health impact assessment (HIA) is a robust approach for evaluating the adverse health efects of air pollution on a population, particularly on socioeconomically deprived people [34]. Utilizing quantitative, qualitative, and participatory approaches, this strategy is applicable to numerous economic sectors. Te Benefts Mapping and Analysis Program-Community Edition (BenMAP-CE) of the Environmental Protection Agency is a helpful tool for HIA. It is typically used to assess the impact of air pollution on human health. For example, Mueller et al. [35] used the PM 2.5 concentrations observed from ground-based measurements in Tailand from 1996 to 2016 to estimate the economic and health impacts of long-term exposure to ambient PM 2.5 in the Tai population using BenMAP. Fold et al. [36] used BenMAP to examine annual morbidity associated with PM 2.5 in Bangkok, Tailand, from 2012 to 2018. Nguyen et al. [37] used BenMAP to estimate the public health and economic impacts of PM 2.5 exposure in Mainland Southeast Asia (MSEA).
To elucidate and emphasize the disease burden caused by particle air pollution, we reveal the fndings of a health impact assessment (HIA) conducted using BenMAP-CE in eight northern Tai provinces. Te HIA generated estimates of the amount of respiratory illness mortality in northern Tailand attributable to PM 10 exposure. First, we analyzed a situation in which the PM 10 daily mean was reduced by 120 μg/m 3 , and then, we described a scenario in which the PM 10 daily mean was reduced to the WHO-AQ standard (45 μg/m 3 ).

Methodology
To study the efects of PM 10 on the health of people in northern Tailand, we used daily PM 10 concentration data from eight ground-based measurement sites from the Tai Pollution Control Department in the year 2012 as input data for the U.S. Environmental Protection Agency's Benefts Mapping and Analysis Program-Community Edition (BenMAP-CE). Two hypothetical scenarios for reducing PM 10 concentration were evaluated in this study. In both scenarios, the excess O 3 concentration was rolled back to the EPA's standard level of ≤0.070 ppm (using the percentage rollback method in BenMAP-CE). In the frst scenario, the excess PM 10 concentration was rolled back to the daily Tailand air quality guidelines (120 μg/m 3 ); meanwhile, in the second scenario, it was rolled back to the daily WHO air quality guidelines (45 μg/m 3 ).

General Information of BenMAP-CE.
BenMAP is an efective HIA tool. It was published in 2003 and is the primary tool used by the United States Environmental Protection Agency (EPA) to quantify the health and economic benefts of achieving the future National Ambient Air Quality Standards (NAAQS) [38,40]. BenMAP-CE is identical to the previous version utilized by the United States Environmental Protection Agency for a range of strategy assessments.

Study Area and Air Pollution Data.
In this study, we used the observed PM 10 data from eight locations (Lampang, Chiang Mai, Nan, Lamphun, Phrae, Chiang Rai, Phayao, and Mae Hong Son) from the Tai Pollution Control Department in northern Tailand between the years 2010 and 2020 ( Figure 1). Te quality of the data was analyzed using the standard method, as described by Wong et al., [41]. Te percentage of missing data was in the range of 0.80%-20.10% during the years 2010-2020 (Table 1). We found a number of days on which the Tailand 24-hour guideline (120 μg/m 3 ) was exceeded, particularly in the years 2010, 2011, and 2012, as well as in 2016, 2019, and 2020. Te daily average of PM 10 concentration in northern Tailand was in the range of 36.1-47.5 μg/m 3 during the years 2010 and 2020. Te highest number of days exceeding Tailand's air quality standard and mortality rate were 175 days and 0.32, respectively, in 2012, with an acceptable missing data rate of 8.50% and an average PM 10 of 47.5 ± 4.4 μg/m 3 in northern Tailand. As a result, we selected the year 2012 as the case study in this work.

Estimating Human Health Impacts.
To estimate the impacts of PM 10 on human health, equation (1) was used to calculate the number of individuals who avoided death (US EPA 2018):  where ΔPM is the change in air quality, i.e., the diference between the baseline air pollution level and the air pollution level after some controls. Pop is the number of people in northern Tailand who are at risk of becoming exposed to PM 10 and who are aged 18 and above, as listed in Table 2.
Meanwhile, the health efect estimate (β) is based on the following equation: where β is a percentage change in the risk of signifcant health efects produced by a one-unit increase in ambient air pollution.
In terms of epidemiological studies linking shortterm PM 10 exposure to mortality in northern Tailand, the epidemiology was derived from the relative risk (RR) value taken from a previous study by [42], as given in Table 2. Tey performed a cross-sectional study between March 2016 and March 2018 (a total 761 days) in Chiang Mai province in northern Tailand. A time-series analysis was used to examine associations between air pollution levels and changes in mortality (specifcally, nonaccidental mortality and cardiopulmonary diseases) for a study population. To assess the lag structure between daily average concentrations of PM 10 and daily respiratory disease, they examined separate models for each lag from 0 to 7 days prior to the events. A lag time of zero (lag 0) was defned as same-day exposure to PM 10 . Finally, the adjusted RRs with 95% confdence intervals (CI) from regression analysis were estimated for each 10 μg/m 3 increment of PM 10 [43]. In this study, we used the RR values at lag 6, which is the statistical signifcance level (<0.05) (adjusted RR � 1.069).
Finally, the health baseline incidence (Y 0 ) is an estimate of the typical number of fatalities in a particular year (U.S. EPA, 2018). It was calculated from the ratio of the number of cases of mortality from respiratory diseases to the total population, as listed in Table 3. Te Y 0 was estimated using the following equation: 10 in Northern Tailand. Figure 2 illustrates the monthly average of PM 10 concentrations from eight locations in the study areas. Most of the time, the concentration of daily PM 10 in northern Tailand did not exceed the daily standard set by the Pollution Control Department (PCD), which is 120 μg/m 3 . However, the results suggest that there was a 300 μg/m 3 spike reported in the study areas in March. Tis is because of the huge amount of biomass that is burned in northern Tailand [44] Furthermore, the infuence of transboundary particulate emissions from surrounding countries, such as Myanmar and Laos, might boost the peaks of PM 10 [11]. Te decrease in PM 10 concentrations for the eight stations begins in April and ends in November. It increased somewhat in December. Te low PM 10 concentrations in July and August were caused by the high rainfall rates across northern Tailand, where the southwest monsoon was active. Precipitation and deposition can wipe away particulate matter that is suspended in the atmosphere. Te annual average PM 10 concentration ( Figure 3) ranged from 43 to 61 μg/m 3 , with the highest and lowest concentrations of 61 and 43 μg/m 3 , respectively. Table 4 shows a descriptive analysis of the studied population's demographic characteristics, hospital admission outcomes, mortality rate from respiratory disease, and the average PM 10    admission to IPD for respiratory disease exacerbation were registered in Chiang Rai, Nan, and Mae Hong Son for 2012 (Table 4). When considering the total population, the Nan and Mae Hong Son provinces had the highest IPD admission rates, with values of 2.57% and 4.35%, respectively. Te mortality rate from respiratory disease was in the range of 0.26-0.40. Te exceeding of standard PM 10 concentrations was likely associated with an increase in the risk of respiratory disease-related hospital admissions which is similar to that reported by Pini et al. [45] who reported that an increase in short-term exposure to particulate matter (PM 2.5 and PM 10 ) was strongly associated with a higher risk of emergency department (ED) admission and hospitalization. Te highest mortality rate was found in Phayao province, with a value of 0.40, while Chiang Rai and Lampang also had high mortality rates, with values of 0.37 and 0.34, respectively. When we addressed a specifc respiratory disease, there were high IPD rates from chronic lower respiratory diseases in those provinces, with values of 38.52%, 40.99%, and 43.87% in Phayao, Chiang Rai, and Lampang provinces, respectively. Chronic lower respiratory disease was associated with an increase in mortality related to PM 10 , along with chronic obstructive pulmonary disease and pneumonia [46]. Table 5 presents the avoided mortalities from respiratory diseases due to PM 10 exposure in northern Tailand. In eight provinces of northern Tailand, the avoided impacts in terms of respiratory mortality of a daily mean concentration of PM 10 were in the range of 2-18 (95% CI: 1-30) cases per year (rollback to 120 μg/m 3 ) and 4-47 (95% CI: 1-76) cases per year (rollback to 45 μg/m 3 ). When the daily PM 10 concentration was reduced to 120 μg/m 3 , the attributable risk percentage for respiratory disease mortality decreased by 1%-5%. When PM 10 concentrations were reduced to 45 μg/m 3 , the attributable risk percentage for respiratory disease mortality in northern Tailand changes from 1% to 12%.

Health Impact Assessment.
Te Health Impact Assessment for northern Tailand indicated that reducing the annual mean levels of PM 10 would result in signifcant health benefts. Notably, complying with WHO-AQG for PM 10 (45 μg/m 3 ) would result in substantial reductions in respiratory disease mortality. Te number of preventable fatalities doubles with a reduction scenario level of 45 μg/m 3 compared to a reduction scenario level of 120 μg/m 3 . Tis result is comparable to that of other studies, such as [47], who evaluated the annual health implications of particulate matter (PM) by reducing the annual mean PM 10 concentration to 20 μg/m 3 in 27 cities in Southeast and East Asia in 2009. Although the second scenario of compliance reduction difers from Yorifuji et al. [47], the results of an 8% reduction in mortality in 27 Southeast and East Asian cities are comparable. PM 10 has an efect on respiratory illness mortality; however, other pollutants, such as NO 2 , PM 2.5 , O 3 , and CO, are also associated with respiratory mortality. Pothirat et al. [38] revealed that PM 2.5 was related to acute exacerbations of chronic obstructive pulmonary disease (AECOPD), while CO, O 3 , and SO 2 were related to visits to the emergency room (ER) for community-acquired pneumonia (CAP). Meanwhile, O 3 , NO 2 , and SO 2 were correlated with heart failure (HF), myocardial infarction (MI), and cerebrovascular accident (CVA), respectively. According to the WHO [48], levels of PM exposure in Asian cities vary substantially. Nonetheless, the HIA analysis indicated that air pollution had a signifcant efect on public health in areas with comparatively high levels of air pollution and sizable populations. Tis conclusion implies that the public health implications of air quality in metropolitan areas with low to moderate exposure levels should not be disregarded. From

Conclusion
Te purpose of this study was to analyze the annual health efects of particulate matter (PM) less than 10 μm in diameter (PM 10 ) in northern Tailand in the year 2012. Te BenMAP-CE program was used as a tool for evaluating the health impact of PM 10 in northern Tailand. PM 10 concentration data collected from the Pollution Control Department (PCD) were used as the input data for BenMAP-CE. Te results show that the annual average PM 10 concentration was in the range of 43-61 μg/ m 3 , with a peak-observed PM 10 concentration of 300 μg/ m 3 in March. We further evaluated the efects of PM 10 exposure in northern Tailand and found that, when the PM 10 concentration is reduced to 120 μg/m 3 , the efects on respiratory mortality tend to decrease by up to 5%. When the PM 10 concentration was decreased to 45 μg/ m 3 , the adverse efects on respiratory mortality were reduced by up to 12%. According to the fndings of this study, lowering the annual mean levels of PM 10 would result in signifcant health benefts. Compliance with WHO-AQG for PM 10 (45 μg/m 3 ) would result in signifcant reductions in respiratory disease mortality. Current air pollution levels in northern Tailand have a nonnegligible public health impact.

Data Availability
Te data generated or analyzed during this study are included within the article. Te observation data used in this study were provided with permission by the Pollution Control Department (PCD) for pollution data and the Department of Disease Control (DDC) of Tailand for mortality data and hence cannot be made freely available. Access to these data can be obtained by contacting the PCD at https://www.pcd.go.th/ and DCC at https://ddc. moph.go.th.

Conflicts of Interest
Te authors declare that they have no conficts of interest. Journal of Environmental and Public Health 7